【NEC】 523 Magnetic Drum Unit

NEC completed the 523 magnetic drum unit as an external memory for the NEAC-2230 and NEAC-2206, and exhibited it as part of the NEAC-2230 and NEAC-2206 at the first Japanese-made electronic computer show in November 1962.
This unit housed an IR-812 magnetic drum unit together with electronic circuits for writing, reading, band selection and other tasks.
NEC also completed the IR-811 magnetic drum unit which used the same magnetic drum, but expanded memory capacity by increasing the number of tracks and improving the recording system.
(The photo does not show the 523 magnetic drum unit. It shows the IR-811 magnetic drum unit which used the same magnetic drum.)

Specifications of IR-811 and IR-812 Magnetic Drum Units
Model name IR-811 IR-812
(Use in 523 Magnetic Drum Unit)
Drum dimensions(mm) 320ø×365 320ø×365
Rotation speed(rpm, at AC60Hz) 3500 3500
Number of information tracks 250 200
Memory capacity in 1 cycle(bit) 7,000 3,250
Total memory capacity(bit) 1,750,000 650,000
Applications - NEAC-2230,NEAC-2206

  
IR-811 Magnetic Drum